This invention relates to a direct current motor having a wound armature provided with a plurality of insulated windings.
It is well known that a direct current (DC) motor, provided with a plurality of armature windings formed in a lap winding manner or a wave winding manner, is highly efficient and has better commutating characteristics as the number of armature windings increases. However, if the conventional manner of lap winding or wave winding is employed in a coreless motor, the armature will increase in thickness because the armature windings are superposed on each other in many layers. The increased thickness of the armature will substantially reduce the effective magnetic field of the field magnet which passes through the armature resulting in decreased motor efficiency and starting torque. In order to solve these problems, the prior art effort has been directed to reduce the thickness of the conductor portions, which contribute to generate torque, by specially processing the edge portions of the coils. This processing for reducing the thickness of conductor portions was performed by press molding, and accordingly was often accompanied by such defects as breaking and short-circuiting of the armature windings. Further, since the phase relationship between the armature windings could not be positively held in a desired state at the time the windings were arranged, correct phase relationship between the windings was liable to be distorted. It was, therefore, very difficult to obtain a DC motor having an efficiency as high as theoretically expected. Accordingly, such prior art DC motors were costly and could not be mass produced. Another prior art technique used for conventional cylindrical coreless DC motors, for avoiding superposition of the edge portions of coils of armature windings on each other required that insulated wire be wound in alignment, turn by turn, so that the entire width of winding, or a part thereof, may slant with respect to the rotating axis. This technique, however, also cannot be used for mass-production and is costly.